1. Field of the Invention
This invention relates to an electronically controlled automatic speed changing apparatus capable of skip speed changing.
2. Description of the Prior Art
Prior art electronically controlled speed changing apparatus of the type referred to above is constructed such that the speed is changed stepwisely in the shift-up direction or shift-down direction by operating a speed changing clutch mechanism for changing meshing of gears.
Such speed changing clutch mechanism, however, requires a certain time until it is completely engaged due to a time for filling pressurized oil in a clutch chamber and due to an oil pressure modulation (a modulation necessary for gradually changing oil pressure), etc. For this reason, it has been the practice to set a definite time (called a speed change inhibition time) necessary to complete the clutch engagement as a speed changing time for inhibitting the speed change to a next stage until this time has elapsed.
Where the automatic speed changing apparatus is operated in the shift-down direction when a car running at a high speed reaches a steep slope, the prior art speed changing apparatus has the following defects.
More particularly, since the driving torque of the car becomes zero before the speed changing clutch mechanism actually engages so that the car speed decreases during this interval. Accordingly, when the car reaches the steep slope while it is running at the 7th speed, the car speed would change stepwisely, that is, 7th speed.fwdarw.6th speed.fwdarw.fifth speed.fwdarw.fourth speed. This not only decreases the operating life of the elements constituting a power line but also gives to an operator unconfortable feeling caused by shocks due to speed changing.